Most yo-yos are in the form of two disk-shaped side members that are rigidly connected to each other by some type of axle structure. The axle structure may be an assembly of multiple parts, or merely be in the form of a dowel or a riveted pin, and may be made of metal and/or wood and/or plastic. In many modern yo-yos, the axle structure includes a center-located bearing or other member that is rotatable on an elongated axle member.
The axle structure also forms an anchor for one end of a string-type tether. An end-located loop portion of the tether is positioned so that it encircles a center portion of the axle structure. The free end of the tether is usually tied to create a second loop portion that can be placed about one of a user's fingers to thereby secure the yo-yo to the user.
When the tether is wound about the axle structure and the yo-yo is released or thrown from the user's hand, the yo-yo will begin to rapidly spin as it moves away from the user's hand and the tether unwinds from the axle structure. Once the tether is fully unwound, the yo-yo may “sleep” at the end of the tether, whereby the yo-yo continues to spin without the tether rewinding on the axle structure. Once the yo-yo is sleeping, there are a number of tricks, such as “walk the dog,” that a person can perform with the spinning yo-yo. A sleeping yo-yo is also often used to perform tricks where the spinning yo-yo is temporarily placed upon a portion of the tether intermediate of the tether's two ends.
At the completion of most yo-yo tricks, the user will make a rapid tug/jerk on the tether. This will result in a brief tightening of the tether, which is then automatically followed by a temporary slackening of the tether. Once the tether goes slack, the tether's twist will cause one or more portions of the tether located proximate the axle structure to move, and thereby contact a spinning portion of the yo-yo. Once contact has occurred, the tether portion can become snagged on, or otherwise engaged to, a spinning portion of the yo-yo in a manner whereby rotation of the spinning portion of the yo-yo causes the tether to wind about the axle structure. Winding of the tether on the axle structure causes the yo-yo to return to the user's hand.
There are three crucial performance characteristics of a yo-yo that enable a user to perform yo-yo tricks. The yo-yo must be capable of sleeping for an extended period of time, it should return on command, and it should be smooth on the tether.
Concerning a yo-yo's sleep time, the longer the yo-yo can be made to sleep, the more time the user will have to complete any particular yo-yo trick that requires the use of a sleeping yo-yo. It is well known that by minimizing friction in the yo-yo's components, one can maximize the yo-yo's sleep time. Also, a heavy yo-yo will usually sleep longer than a light one. Furthermore, it is known that whenever the tether even slightly rubs against a spinning portion of the yo-yo, the created friction will reduce the yo-yo's sleep time.
For a yo-yo to return on command, the structure and design of the yo-yo must be such that when the user causes the tether to briefly go slack, a portion of the tether can become snagged on a spinning portion of the yo-yo and thereby cause the yo-yo to return to the user's hand. A yo-yo's responsiveness is hereby defined as the ease with which one can cause the yo-yo to return on command. Responsiveness is also commonly defined by how sensitive the yo-yo is to any contact between the tether and a spinning portion of the yo-yo when the yo-yo is sleeping. A yo-yo can be considered too responsive if the yo-yo returns to the user's hand without the user knowingly causing, or wanting, said return to occur. When such an inadvertent return does happen, the performance of a yo-yo trick will usually be cut short and thereby ruined.
A yo-yo's responsiveness is usually enhanced through the use of particular engagement adaptations, such as raised ribs, on the tether-facing surface of the yo-yo's side members. The tether-facing surface of a side member is herein defined as the surface of the side member that faces a portion of the yo-yo's tether when said tether extends outwardly from the yo-yo. Additionally, a yo-yo's ability to return on command is directly related to the yo-yo's weight, with a light yo-yo usually being easier to get to return than a heavy one. The yo-yo's string gap and axle structure can also affect the yo-yo's ability to return on command. A yo-yo's string gap is herein defined as the area located between the yo-yo's side members.
Concerning a yo-yo's ability to be smooth on the tether, this refers to a yo-yo's ability, when it is sleeping at the end of the tether, to be temporarily placed on a medial portion of the tether without the tether snagging on a spinning portion of the yo-yo. An example of a trick that requires a yo-yo to be smooth on the tether is “man on the trapeze.” If, during such a trick, the yo-yo can slide on the tether, the yo-yo is said to be very smooth on the tether/string. The ability of a yo-yo to be smooth on the tether is favored when the yo-yo's responsiveness is low.
One other important consideration involved in the design/performance of a yo-yo is the wear rate of the yo-yo's tether and the portion(s) of the yo-yo that engage said tether. Wear occurs whenever the tether contacts a spinning portion of the yo-yo. While it is easy to replace a tether, replacement of the structure that engages the tether is usually impossible. Once significant wear occurs in the yo-yo's structure, the yo-yo's performance degrades and the yo-yo eventually becomes unusable.
The design of a yo-yo typically involves trade-offs. A yo-yo having physical attributes that make it smooth on the string, such as a wide string gap and a less aggressive tether engagement surface, will normally make the yo-yo less responsive and therefore harder to make return. A very responsive yo-yo, with a narrow string gap and aggressive tether engagement surfaces, may not sleep for a long time and may experience rapid tether wear.
It is not unknown in the prior art to provide ways for a user to change a yo-yo's physical characteristics to thereby change the yo-yo's performance characteristics. The most common method is to provide the yo-yo with structure that enables a user to change the size of the yo-yo's string gap. BY increasing the size of the gap, one can change a yo-yo that will readily return on command to instead be less responsive but be smoother on the tether.
In most conventional yo-yo's, adjustable string gap is accomplished via the yo-yo's axle structure and side member securement method. Both side members are normally threadedly engaged to the axle structure whereby a user can rotate one of the yo-yo's side members relative to the other to thereby change the spacing/string gap between the side members. However, repeated relative movements of the yo-yo's side members can wear out the adjustment apparatus. In addition, this form of adjustment is extremely inexact whereby a yo-yo may require multiple repetitions of the adjustment process before the yo-yo exhibits the desired level of responsiveness. Furthermore, a basic adjustable string gap yo-yo does not allow a user to change the responsiveness of a yo-yo without changing its string gap.
McAvoy teaches in U.S. Pat. No. 5,254,027 a different method for changing a yo-yo's characteristics. He makes use of a moveable lapper disk in each side member. The lapper disk has a tether-facing surface that is flat, smooth and is designed to continually contact the tether. However, the fastener that pushes on the lapper disk does not provide a positive engagement for bi-directional movement of the disk. In addition, the flat, smooth tether-facing surfaces contacting the tether can cause a decrease in the yo-yo's sleep time, an increase in tether wear and may require a user to spend significant time trying to adjust the lapper disks to accomplish a desired change in the yo-yo's responsiveness.
Most prior art yo-yos have designs that limit their versatility. For example, a beginning yo-yo player will pick a highly responsive yo-yo to ensure that it will be easy to get the yo-yo to return on command. A more experienced player wishing to perform string tricks in which smoothness on the string is desirable will normally choose a less responsive yo-yo with a wide string gap. The prior art adjustable yo-yos, while enabling some changes in performance, do not provide a desired level of all-around performance. As a result, many yo-yo players will own a multitude of yo-yos so that he or she can pick the yo-yo having the best mix of characteristics for the performance of any particular trick. However, owning a multitude of yo-yos is costly, and transporting a large number of yo-yos can be bothersome.